Objective：To investigate the clinical value of quantitative measurements of extraocular muscles with T2 mapping in the diagnosis and staging of thyroid-associated ophthalmopathy（TAO）. Methods：Thirty-six patients with TAO and 28 healthy controls（HCs）were enrolled in our study and evaluated using T2 mapping imaging. The hotspot T2 relaxation time（T2RT）values of the most inflamed extraocular muscles were measured，and compared between the TAOs and the HCs groups，as well as the active TAOs and the inactive TAOs groups. Receiver operating characteristic（ROC）analysis was performed to evaluate the diagnostic value of T2RT for discriminating active TAOs from inactive TAOs. Results：The T2RT values of extraocular muscles in TAOs were significantly higher than those in HCs（P < 0.001）. The T2RT values of extraocular muscles in active TAOs were significantly higher than those in inactive TAOs（P < 0.001）. ROC results indicated that，optimal staging efficacy（area under the curve，0.863；sensitivity，75.0%；specificity，93.8%）for differentiating active TAOs from inactive TAOs could be obtained，when setting 116.5 ms as the cutoff T2RT value of extraocular muscles. Conclusion：Quantitative measurements of extraocular muscles with T2 mapping could assist in the diagnosis and staging of TAO.